Conventional methods of body fluid identification use a variety of labor-intensive, technologically diverse techniques that are performed in a series, not parallel, manner and are costly in terms of time and consumption of sample. It used to be standard practice to perform biochemical, serological, and immunological tests to identify the body fluid(s) comprising a biological stain. Increasingly, however, classical methods for body fluid identification have no confirmatory technique for some frequently encountered body fluids. For example, there is no definitive test for the presence of saliva or vaginal secretions, and urine identification can be problematic. The need exists for a more reliable, efficient assay system to supplant conventional methods for body fluid identification.
Previous research in the development of a ribonucleic acid (RNA) based assay system for the identification of body fluids, included considerations for the use of protein and messenger RNA (mRNA) since both are expressed in a tissue-type specific manner. However, multiplex analysis of complex protein mixtures, such as those present in body fluid stains, requires further developments in the field of proteomics. Whereas, with messenger RNA (mRNA), the molecular intermediate between genetic DNA and expressed protein is at present, supported by technologies for massively parallel analysis in the field of genomics.
As reported by B. Alberts, et al. Molecular Biology of the Cell 3rd ed., Garland Publishing Inc., NY, 1994, a pattern of gene expression is produced that is unique to each cell type and is evinced by the presence as well as the relative abundance of specific mRNAs. Each cell type, such as, blood monocytes, lymphocytes, ejaculated spermatozoa, epithelial cells lining the oral cavity or epidermal cells, has a unique pattern of gene expression.
Specific gene expression patterns for saliva were reported by J. Juusola and J. Ballantyne in February 2002 in a presentation to the American Academy of Forensic Science (AAFS) entitled, “The Development of an RNA Based Assay System for Body Fluid Identification,” and in Forensic Science International, Vol. 135 (2003) pages 85-96 (“Messenger RNA Profiling: a Prototype Method to Supplant Conventional Methods for Body Fluid Identification”). Semen specific genes were reported by J. Juusola and J. Ballantyne in “The Development of an RNA Based Assay System for Body Fluid Identification,” presented to AAFS, February 2002. M. Bauer and D. Patzelt also identified semen specific genes in an article, “Protamine mRNA as Molecular Marker for Spermatozoa in Semen Stains,” International Journal of Legal Medicine Vol. 117 (2003) pages 175-179.
As more and more tissue-specific genes (mRNAs) are identified for use in the positive identification of body fluids and tissues of forensic importance, there is an increasing need for a device or assay system that provides simultaneous and semi-automatic analysis through a common assay format. The novel multiplex, parallel assay system of the present invention provides a common assay format and offers many advantages over the conventional analysis procedures for body fluid identification.